The present invention relates to a liquid sealing type body mount provided between a body of a vehicle and a frame on a support side such as in a suspension or the like in order to support the body in a vibration-proof manner.
Heretofore, a body mount used in a rear suspension of a vehicle such as an automobile has been known in which there are provided an inner cylinder coupled to one of a body of the vehicle and a suspension-side frame for supporting the body, and an outer cylinder coupled to the other of them. The inner and outer cylinders are joined to each other by a rubber elastomer provided between them. Two liquid chambers, which are formed at portions opposed to each other with the aforesaid inner cylinder between, are provided between the inner and outer cylinders. The liquid chambers are communicated with each other by an orifice passage to obtain a vibration damping effect by liquid fluid effect between the two liquid chambers (for example, as shown in Japanese Patent Laid-Open Nos. Hei 2-38730 and Sho 62-188832).
However, in this conventional kind of body mount, it is general that a rubber portion forming an end wall in an axial direction of the aforesaid liquid chamber forms a right angle to an axis of the device.
In case that the thus structured mount is used with the aforesaid liquid chambers positioned respectively in front and back directions of the vehicle, a stable vibration-proof characteristic is obtained in some degree in upper and lower directions where the load of the body is applied, due to an effect of the decrease of moving spring constant. However, in front and back directions where a large vibration is applied at a time of acceleration, such as the starting time or at the braking time, the vibration damping effect becomes small due to rigidity of the rubber portion of the end wall of the aforesaid liquid chamber. For example, in the case that an attenuation coefficient at a frequency of 15 Hz is set to about 4Nxc2x7s/mm, a moving spring constant at about 100 Hz becomes 2000N/mm and more, so that sufficient vibration-proof function does not act. Therefore, improvement is further desired.
The present invention has been made in view of the forgoing. Its objective is to provide a liquid sealing type body mount in which, with respect to vibration mainly in the front and back direction, for example, an attenuation coefficient at a frequency of 15 Hz is set to about 4Nxc2x7s/mm, and a moving spring constant at about 100 Hz can be reduced to as low as about 1000N/mm, so that a sufficiently vibration-proof characteristic can be obtained.
The invention provides a liquid sealing type body mount provided between a body of a vehicle and a frame in order to support the body in a vibration-proof manner. The body mount comprises an inner cylinder fixed to one of the aforesaid body and a frame, an outer cylinder fixed to the other of them, a rubber elastomer that is provided between the inner and outer cylinders and which couples them to each other, two liquid chambers, which are formed at portions of the rubber elastomer opposed to each other with the aforesaid inner cylinder therebetween and formed between the inner and outer cylinders, and an orifice passage for communicating the liquid chambers with each other. Further, in the body mount in which a load input of the body is performed in the axial direction thereof, end walls in the axial direction in the aforesaid liquid chambers are formed of a rubber film which is a part of the aforesaid rubber elastomer, and the rubber film is formed aslant from the inner cylinder side toward the outer cylinder, that is, outward in the axial direction.
According to the above body mount, when vibrating power orthogonal to the axial center acts in the opposite direction of the two liquid chambers, since the rubber films forming the end walls in the axial direction of the liquid chambers are formed aslant, the vibration can be damped effectively by action of this rubber film. For example, at a frequency of 15 Hz, with a vibration coefficient of about 4Nxc2x7s/mm, the moving spring constant can be reduced to as law as about 1000N/mm. Therefore, by using this body mount with the aforesaid liquid chambers positioned in the front and back directions of the vehicle, a good vibration-proof characteristic in relation to the vibration in the front and back directions and obliquely in the front and back directions can be obtained.
In the aforesaid body mount, it is particularly preferable that an angle of inclination of the end wall composed of the aforesaid rubber film in relation to the axial center is 15xc2x0 to 70xc2x0.
Namely, in case that the angle of inclination is over or below the aforesaid range, the rigidity balance in the direction perpendicular to the axis and in the axial direction is lost respectively, and a bad influence is given to the vibration transmission in each direction. Therefore, it is preferable to set the angle of inclination in the aforesaid range, more preferably in a range of 30xc2x0 to 69xc2x0.
In the aforesaid liquid sealing type body mount, the end walls, composed of the rubber films, extend from the inner cylinder side in the radial direction in substantially wavy shape to the outer cylinder in a direction expanded axially outward. In this case, similarly to the foregoing, the moving spring constant is reduced, and further a free length of the rubber film is extended to improve durability.
Further, it is preferable that the thickness of the end wall composed of the aforesaid rubber film is 2 to 6 mm. If the thickness of the end wall of the aforesaid rubber film is too thin, the pressure transmission efficiency of liquid decreases, so that the effect of liquid seal is difficult to produce. If the rubber film is too thick, the rigidity of the rubber portion increases and the vibration transmission to the liquid pressure decreases, so that the effect of liquid seal is difficult to produce.
Further, it is preferable that stoppers extending from the inner cylinder in the radial direction are provided in both the liquid chambers. The stopper prevents larger displacement than a predetermined displacement.
Particularly, it is preferable that the aforesaid stopper is formed by embedding a metal portion fixed to the inner cylinder in a rubber portion formed integrally with the rubber elastomer such that shock is softened when the stopper operates.
It is particularly preferable that an opening angle in the circumferential direction of the aforesaid liquid chamber is not less than 60xc2x0 and not more than 140xc2x0 since the area of the axial end wall of the rubber film can be made large and durability can be improved.